| From: Baoquan He <bhe@redhat.com> |
| Subject: mm/vmalloc: fix the unchecked dereference warning in vread_iter() |
| Date: Wed, 18 Oct 2023 22:50:14 +0800 |
| |
| LKP reported smatch warning as below: |
| |
| =================== |
| smatch warnings: |
| mm/vmalloc.c:3689 vread_iter() error: we previously assumed 'vm' could be null (see line 3667) |
| ...... |
| 06c8994626d1b7 @3667 size = vm ? get_vm_area_size(vm) : va_size(va); |
| ...... |
| 06c8994626d1b7 @3689 else if (!(vm->flags & VM_IOREMAP)) |
| ^^^^^^^^^ |
| Unchecked dereference |
| ===================== |
| |
| This is not a runtime bug because the possible null 'vm' in the |
| pointed place could only happen when flags == VMAP_BLOCK. However, the |
| case 'flags == VMAP_BLOCK' should never happen and has been detected |
| with WARN_ON. Please check vm_map_ram() implementation and the earlier |
| checking in vread_iter() at below: |
| |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| /* |
| * VMAP_BLOCK indicates a sub-type of vm_map_ram area, need |
| * be set together with VMAP_RAM. |
| */ |
| WARN_ON(flags == VMAP_BLOCK); |
| |
| if (!vm && !flags) |
| continue; |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| |
| So add checking on whether 'vm' could be null when dereferencing it in |
| vread_iter(). This mutes smatch complaint. |
| |
| Link: https://lkml.kernel.org/r/ZTCURc8ZQE+KrTvS@MiWiFi-R3L-srv |
| Link: https://lkml.kernel.org/r/ZS/2k6DIMd0tZRgK@MiWiFi-R3L-srv |
| Signed-off-by: Baoquan He <bhe@redhat.com> |
| Reported-by: kernel test robot <lkp@intel.com> |
| Reported-by: Dan Carpenter <dan.carpenter@linaro.org> |
| Closes: https://lore.kernel.org/r/202310171600.WCrsOwFj-lkp@intel.com/ |
| Cc: Lorenzo Stoakes <lstoakes@gmail.com> |
| Cc: Philip Li <philip.li@intel.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| mm/vmalloc.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/mm/vmalloc.c~mm-vmalloc-fix-the-unchecked-dereference-warning-in-vread_iter |
| +++ a/mm/vmalloc.c |
| @@ -3809,7 +3809,7 @@ long vread_iter(struct iov_iter *iter, c |
| |
| if (flags & VMAP_RAM) |
| copied = vmap_ram_vread_iter(iter, addr, n, flags); |
| - else if (!(vm->flags & VM_IOREMAP)) |
| + else if (!(vm && (vm->flags & VM_IOREMAP))) |
| copied = aligned_vread_iter(iter, addr, n); |
| else /* IOREMAP area is treated as memory hole */ |
| copied = zero_iter(iter, n); |
| _ |
